1. Field of the Invention
The present invention relates generally to a home network, and more particularly, to a method and apparatus for determining an object updates in a media service by using a Content Directory Service (CDS) of Universal Plug and Play (UPnP).
2. Description of the Related Art
UPnP is a protocol capable of discovering and controlling electric appliances connected to a network, and is a standard technique of home networking. In particular, UPnP Audio/Video (AV) is a technique for using multimedia content, such as AV, through the network based on the UPnP. Generally, a UPnP AV system includes a media server, a media renderer, and a controller for controlling the media server and the media renderer. The media server provides a multimedia file by using a CDS. The media renderer reproduces the multimedia file provided from the media server. The controller provides control such that the media server and the media renderer can operate through interoperations. Herein, CDS indicates a service included in the media server. CDS manages content on an object basis. Each object has several pieces of information, i.e., properties, for representing the object.
A plurality of media servers can be present in one home network. The plurality of media servers can have different content. Accordingly, there is a need for a method capable of easily synchronizing the media controller with the different media servers in order to receive content distributed in the different media servers from the perspective of a conventional UPnP AV user. In particular, when content is newly added or modified in a media server, there is a need for a method in which the media controller detects the addition or modification of the content and announces the detection result to the users. For example, there is a need for a method in which a tag “New” is set to a newly added object in the media server, a tag “Modified” is set to a modified object, and the tag “New” and the tag “Modified” are both set to a newly added and modified object so that the users can easily recognize the added or modified objects.
Accordingly, a 3rd version of UPnP CDS provides a function by which the media controller can identify addition, deletion, and modification for objects of the media server. In this method, an object update identifier (objectUpdateID) is set for each object in the media server, and thereafter when an object change occurs, the objectUpdateID is updated so that the media controller can identify whether the object is added and modified.
FIG. 1 illustrates a conventional method in which content is added using a CDS.
Referring to FIG. 1, a media server 100 stores three objects. In this case, an objectUpdateID is mapped to each object. The objectUpdateID is set to a value greater than that of a previous object according to an addition order. In this case, when a media controller 110 accesses the media server 100, the media controller 110 stores a maximum value (i.e., 3) of the objectUpdateIDs mapped to the respective objects as a system update identifier (systemUpdateID) 101. Thereafter, when a new object is added in the media server (as indicated by a reference numeral 103), the media server maps a value 4, which is greater than the objectUpdateID of the previous object to the added object, as an objectUpdateID 105. Accordingly, when the media controller 110 re-accesses the media server 100, the media controller 110 will identify the objectUpdateID 105 having a value greater than the systemUpdateID 101 stored previously, and can determine the object to be a newly added object.
As described above, the 3rd version of UPnP CDS uses the objectUpdateID mapped to each object in order for the media controller to identify addition, deletion, and modification for each object of the media server. However, this method has a problem in that it only indicates if there is a change in the content, but does not identify if the change is an addition an object is added in the media server or if a previously stored object is modified.
FIG. 2 illustrates a conventional method in which content is modified using a CDS.
Referring to FIG. 2, a media server 200 stores four objects. In this case, when a media controller 210 accesses the media server 200, the media controller 210 stores a maximum value (i.e., 4) of the objectUpdateIDs mapped to the respective objects as a systemUpdateID 201. Thereafter, when an object is modified in the media server 200 (as indicated by a reference number 203), the media server 200 sets an objectUpdateID 205 of the modified object to a value 5 which is greater than the objectUpdateID of the previous object. When the media controller 210 re-accesses the media server 200, the media controller 210 will identify the objectUpdateID 205 having a value greater than the systemUpdateID 201 stored previously, and can determine that there is an updated object, i.e., modified or new. However, as described above, because this method is that same as that described in FIG. 1, there is a problem in that the media controller 210 cannot identify whether the updated object is a newly added objected or a modified object.
FIG. 3 illustrates a conventional method for determining whether content is added or changed in a CDS.
Referring to FIG. 3, when a media controller 310 accesses a media server 300, an object list 311 is acquired and stored together with a systemUpdateID 301. Thereafter, when the media controller 310 re-accesses the media server 300, the media controller 310 determines whether an updated object 305 is present in the stored object list 311, in order to determine whether the updated object is an added object or a modified object. However, this method is problematic in that a large storage space is required because the media controller 310 stores an object list for each of the media servers, and in that it has a relatively high processing time, as the updated object 305 and the stored object list 311 have to be compared one by one.
Accordingly, there is a need for an improved method capable of determining whether an updated object is added, modified, or deleted in the UPnP CDS.